#1 Any downsides to adding this keypad on the outside of the garage to house door
As long as it is in a controlled environment, it should be ok. It is not meant for outdoor use.
Operating temperature: 14 to 131F (-10 to 85C)<
Operating humidity: Up to 93% relative humidity (indoor, dry locations only)
#2 I assume you can see armed or disarmed status on the add on keypad?
Keypad has LED identification for arm or disarm status, no distinction between Away and Stay. However, since its battery operated only, it goes to sleep to save power. You need to tap the keypad to for it to light up. From farther away, you cannot tell the arming status.
What about Audio?
There is no vocal/chime audio, just keypad beeps. Keypad presses will beep, this is optional.
There are distinct beeps for disarm (from IQ Keypad), disarm (from main panel) and beeps for countdown when arming away.
#3 Will the proximity tags work through a wallet? I have several cars
Couldn’t say, its possible depending on the thickness and material of the wallet. Its unlikely to work if you have an anti-RFID wallet. Local testing would be needed.
#4 I assume it will work with my system
Yes, it is compatible. The IQ Keypad is a powerG device but there is the limitation that it only works with IQ Panel 4, IQ 4 Hub, IQ NS, IQ Pro.
It will not work with IQ Panel 2+ even though it has a powerG radio.